In situ Spodumene Li Isotope Ratio Determination by fs‐ LA ‐ MC ‐ ICP ‐ MS : Method Evaluation, Reference Material Development and Geological Applications

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Abstract
Spodumene [LiAl(Si 2 O 6 )], as an important Li source, is crucial for sustaining the global Li supply. Lithium isotopes have been a powerful geochemical tracer for unravelling magmatic‐hydrothermal processes within pegmatite systems. In this study, we systematically evaluated the analytical precision and accuracy of fs‐LA‐MC‐ICP‐MS measurement results for Li isotopes in spodumene samples, with particular emphasis on the accuracy issues arising from non‐matrix‐matched calibration. Compared with glass materials (low‐Li samples), the signal‐matching issue is less significant for spodumene with analytical accuracy within 1.0‰ when the signal‐matching degree ranges from 50% to 300%. Matrix effects between NIST SRM 610 glass and spodumene were found, leading to a ~4.0‰ systematic offset, suggesting that matrix‐matched calibration is necessary for accurate Li isotope determination in spodumene samples. With the refined protocol, the analytical precision and accuracy were better than 1.0‰. Three natural spodumene samples (DHLTan, KKTH and LJG) were characterised as reference materials for in situ Li isotope ratio determination. The three materials have homogeneous δ 7 Li values as revealed by multiple fs‐LA‐MC‐ICP‐MS analyses ( n = 90) in two different measurement sessions. The recommended δ 7 Li values were determined in two or three independent solution MC‐ICP‐MS laboratories, and yielded δ 7 Li values (relative to L‐SVEC) of 1.01 ± 0.46‰ for LJG, 2.69 ± 0.63‰ for DHLTan and 3.63 ± 0.43‰ for KKTH. We applied this technique to the Lhozhag pegmatite‐type Li deposit, and two types of spodumene were identified with first and second stages having δ 7 Li values of ~ ‐6.2‰ and ~ ‐7.5‰, indicating different sources (i.e., hydrothermal fluids).
Funding Information
  • National Key Research and Development Program of China (2024YFC2909304)
  • National Natural Science Foundation of China (42522302)
  • National Natural Science Foundation of China (42273034)
  • Youth Innovation Promotion Association of the Chinese Academy of Sciences (2022066)

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